炭素鋼平滑材の衝撃引張疲労における変形および破損に及ぼす荷重波形の影響

概要

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Impact tensile fatigue tests were performed on smooth specimens of 0.21%C steel m order to investigate the effect of loading wave shape on the deformation and failure. The shape of impact loading wave was characterised by R-value defined as the ratio of the minimum nominal stress to the maximum one in the damping curve of one cycle. R-values employed in the present experiment were -0.17, -0.44, and -0.68. The main results obtained were as follows: (1) The process of the change in residual strain with the number of cycles was found to be divided into two stages, i. e., macrocrack nucleation and its propagation. The residual strain increased with increasing R-value. The strain at fracture for the case of R = - 0.17 was larger than that under static tension, while that for the other cases of R-value was smaller. (2) The compressive residual stress was detected by the X-ray method on the surface of the specimen during impact tensile fatigue. Its absolute value was higher than that induced in static tension, when the residual strains were the same. (3) The following equation was found between the fatigue life N_f and the increment of residua: strain per one cycle Δε^^-_<Rm>. Δε^^-_<Rm>・N_f^n=C The exponent n was independent of R-value, while C varied with R-value.
社団法人日本材料学会の論文
1978-10-15